Change all niccokunzmann/ics-query references to pycalendar/ics-query

[SashankBhamidi]

Change all references from github.com/niccokunzmann/ics-query to github.com/pycalendar/ics-query across the codebase.

[SashankBhamidi]

Things to update:

• pyproject.toml: Homepage, Repository, source_archive, Issues, Changelog URLs
• README.md: CI badge, Polar badge, GitHub Actions link, Polar link
• .github/workflows/tests.yml: release notes Changelog link
• .github/FUNDING.yml: polar: niccokunzmann/ics-query — keep or move?
• CHANGELOG.md: two historical issue links
• ics_query/tests/test_issue_40_valid_calendar.py: docstring link